Fiber optic cables are widely used to transmit and receive data between equipments, and sometimes, even within the same equipment. Fiber optic cables offer several advantages over conventional metal wires, i.e., copper wires. For example, fiber optic cables are resistant to electromagnetic interference and have higher data transmission rates and bandwidth capabilities.
The use of fiber optic cables requires optical signals, which are transmitted through the fiber optic cables, to be converted from and to electrical signals to interface with electrical components that perform various functions, such as encoding, decoding, serializing, deserializing and clock recovery. Thus, optoelectronic equipments require optical transmitters to convert outgoing electrical signal into optical signals to be transmitted on the fiber optic cables and optical receivers to convert incoming optical signals on the fiber optic cables into electrical signal. The optical transmitters and receivers are usually packaged as individual components, commonly known as transmit optical sub-assemblies (TOSAs) and receive optical sub-assemblies (ROSAs), respectively. Typically, a TOSA and a ROSA are assembled together in a fiber optic transceiver module, which can be installed in an optoelectronic equipment. Different types of fiber optic transceiver modules can vary in size and shape, as well as other features of the modules, which usually conform to some standard or Multi-Source Agreement (MSA), such as the MSA for Small Form Factor Pluggable (SFP) transceivers.
A concern with fiber optic transceiver modules is the amount of electromagnetic interference (EMI) emissions generated by the modules. EMI emissions for digital electronic devices are regulated by agencies, such as the Federal Communications Commission (FCC) in US and the International Special Committee on Radio Interference (CISPR) in Europe. Since an optoelectronic equipment can include many fiber optic transceiver modules, the EMI emissions from the fiber optic transceiver modules must be minimized to conform to the required regulations. Furthermore, EMI emissions from fiber optic transceiver modules can interfere with the operation of surrounding electrical components.
Conventional solutions to reduce EMI emissions from a fiber optic transceiver module include placing a metal collar with spring fingers around the module or placing an EMI gasket around the module. However, these metal collars or EMI gaskets may not sufficiently reduce EMI emissions from the modules, and may cause mechanical interaction problems with the cages of optoelectronic equipments into which the modules are placed. Furthermore, since optoelectronic equipments may use differently designed cages, the metal collars and EMI gaskets may not work well for all types of cages. In addition, metal collars are not readily available and must be custom designed, which increases cost and complexity to the manufacturing of the modules.
In view of the above issues, what is needed is a fiber optic transceiver module with an EMI reducing feature that addresses at least some of these issues.